Polynuclear branched tetrazole systems. 2*. New 2-(5-tetrazolyl) ethyl podands and their NH-acidity

Article abstract of DOI:10.1023/B:COHC.0000010646.77507.bb

Nine new polynuclear 2-(5-tetrazolyl)ethyl podands have been obtained by the azidation of the corresponding nitriles. Using Bjerrum distribution functions, the values of pK_a¹, pK_a ², pK_a³, and pK_a⁴ have been determined by a potentiometric method for 14 polynuclear tetrazoles in aqueous and aqueous methanolic solution. The found values lie in the range from 3.5 to 7.5 pH units. The overall rules and the sequence of the ionization of the spatially separated tetrazole fragments in these podand systems are discussed.

Full text of DOI:10.1023/B:COHC.0000010646.77507.bb

Chemistry of Heterocyclic Compounds, Vol. 39, No. 10, 2003
POLYNUCLEAR BRANCHED TETRAZOLE
SYSTEMS. 2*. NEW 2-(5-TETRAZOLYL)ETHYL
PODANDS AND THEIR NH-ACIDITY
V. Yu. Zubarev, E. V. Bezklubnaya, A. K. Pyartman, R. E. Trifonov, and V. A. Ostrovskii
Nine new polynuclear 2-(5-tetrazolyl)ethyl podands have been obtained by the azidation of the
1
2
3
4
corresponding nitriles. Using Bjerrum distribution functions, the values of pKa , pKa , pKa , and pKa
have been determined by a potentiometric method for 14 polynuclear tetrazoles in aqueous and aqueous
methanolic solution. The found values lie in the range from 3.5 to 7.5 pH units. The overall rules and
the sequence of the ionization of the spatially separated tetrazole fragments in these podand systems are
discussed.
Keywords: polynuclear NH-tetrazoles, acidity, multistep ionization, Bjerrum function.
Previously we reported the synthesis of a series of podand (polydentate ligand) systems containing from
two to four 2-(5-tetrazolyl)ethyl fragments in one molecule [1]. The molecular structure and physicochemical
properties of these tetrazole podands enabled their high complex-forming activity in relation to metal ions to be
predicted [1,2]. Efficient filtering materials based on these complexones have been developed recently for the
thorough purification of biological fluids from heavy metals and radionuclides [3]. In connection with the above
the urgent problem is the extension of the series of 2-(5-tetrazolyl)ethyl podands and also a more detailed
investigation of those physicochemical properties of these compounds which will determine their complex-
forming activity.
In the present work we have synthesized nine new polynuclear NH-tetrazoles, differing both in the
number of tetrazole groups and in the chain length separating these terminal fragments. Values of pKa1, pKa2,
pKa3, and pKa4 were determined by a potentiometric method in aqueous and aqueous methanolic solution for the
polynuclear tetrazoles described previously in [1] and for those obtained for the first time in the present work.
Tetrazoles 1-8 were synthesized by the general procedure of [1] by 1,3-dipolar cycloaddition of
dimethylammonium azide to the appropriate nitrile*2. Hydrolysis of the ester groups of the previously reported
ditetrazole 11 leads to the corresponding tetrabasic derivative of malonic acid 9. The initial nitriles were
obtained by the Michael addition [4-7] of the appropriate CH, OH, and NH acids to acrylonitrile (see
Experimental). The structure of the nitriles and of the corresponding tetrazoles was demonstrated by a set of
physicochemical methods.
_______
* For Part 1 see [1].
*2 Tritetrazole 2 was synthesized by the azidation of 3-cyano-3-ethoxycarbonylpimelonitrile with simultaneous
decarboxylation of the ester group.
___________________________________________________________________________________________
Saint Petersburg State Technological Institute (Technical University), Saint Petersburg 198013, Russia;
e-mail: ostrovskii@mail.convey.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10,
pp. 1496-1505, October, 2003. Original article submitted March 19, 2002; revision submitted August 26, 2002.
0009-3122/03/3910-1317$25.00©2003 Plenum Publishing Corporation
1317

N
N
N
N
N
N
N
N
HN
N
HN
NH
O
N
NH
N
N
N
N
N
HN
NH
NH
N
N
N
N
2
N
N
1
N
N
HN
N
N
N
HN
N
N
NH
N
N
N
N
N
N
NH
N
N
N
N
N
NH
NH
NO2
4
3
N
CH
3
N
N
N
NH
O
O
N
NH
HN
N
NH
N
N
N
N
N
N
6
5
N
N
N
N
N
N
N
NH
NH
O
NH
NH
N
N
N
.
HCl
N
NH
7
N
N
O2N
8
N
N
O
OH
N
N
N
N
NO2
NH
NH
N
NH
NH
N
N
N
N
N
HO
O
9
N
NH
N
N
10
CH
3
N
N
N
O
N
N
N
N
O
N
N
HN
NH
O
NH
NH
N
N
O
N
O
HN
NH
H C
3
N
N
N
N
11
N
N
12
1318

N
N
N
N
N
N
N
NH
NH
O
NH
N
N
N
N
N
N
N
NH
N
N
13
14
One of the properties allowing assessment of the ability of these compounds to form complexes is
acidity. Potentiometric titration of compounds 1-14 was carried out in aqueous and aqueous methanolic (when
the water solubility was limiting) solution under conditions of constant ionic strength (0.1 N sodium nitrate
solution). Processing of the titration curves for dihydric acids was carried out by an algebraic method [8], and in
the case of tri- and tetrahydric acids the characteristics of the acid dissociation constants were calculated using a
distribution function (Bjerrum's method) [9,10]. The values calculated in this way for the acid dissociation
constants of tetrazoles 1-14 are given in Table 1. The values of pKa of both the first and second dissociation
stages of tetrazoles 7 and 13, determined in the present work, agreed within the limits of permissible error with
those obtained previously by Latosh and coworkers [11].
Since the pKa values of tetrazoles 1-14 given in Table 1 characterize equilibria in different media it is
difficult to compare them quantitatively [12]. Nonetheless certain generalized qualitative tendencies of the
changes in acid dissociation constants may become apparent depending on the various gradations of structure of
the podand system as a whole. Extremely significant in the present case is the comparison not so much of
absolute values of pKa, as more of a comparison of the differences (∆n) between the size of pKan+1 and pKan (see
Table 1). For all the studied compounds the values ∆1, ∆2, and ∆3 are significantly greater than statistical (the
difference in the values of pKan+1 and pKan in the absence of a mutual electronic influence of the acid
dissociation centers) [13,14]. This indicates that the terminal tetrazole fragments appreciably influence one
another, even at significant mutual separation (five and more sp3-hybridized carbon atoms). Usually the values
of ∆n lie in the range from 0.6 to 1.6 log. units. The exceptions are the ditetrazolylamine 7 and the
ditetrazolylmalonic acid 9, the values for which were appreciably greater and reached 4.6 log. units. This is
explained by the different nature of the ionized fragments (tetrazolyl, ammonium, and carboxyl). It may also be
mentioned that for compounds 2-4 the values of ∆1 were significantly greater than those of all the remaining
polytetrazoles investigated. This observation indicates that the tetrazole ring located at the tertiary carbon atom
dissociates first.
N
N
N
N
_
HN
N
N
N
H+
H+
N
NH
N
NH
N
- H+
- H+
N
N
N
N
N
N
N
N
R
R
NH
N
N
NH
N
N
N
N
_
_
N
N
N
H+
- H+
H+
N
- H+
N
_
N
NH
N
N
N
N
N
N
N
_
_
R
R
N
N
N
N
N
2 R = H, 3 R = Ph, 4 R = 4-O2NC6H4
1319

2
n
∆
TABLE 1. Acid Dissociation Constants of Tetrazoles 1-14* and Values of the Differences Between Them
*
1
2
3
Acids*3
рKа1
рKа2
pKа3
рKа4
∆
∆
∆
s*4
Dihydric NH-acids
9,9-Bis[2-(5-tetrazolyl)ethyl]fluorene (5)
1,2-Bis[2-(5-tetrazolyl)ethoxy]propane (6)
Bis[2-(5-tetrazolyl)ethyl]amide of 4-nitrobenzoic acid (8)
3,3-Bis(ethoxycarbonyl)-1,5-bis(5-tetrazolyl)pentane (11)
1,5-Bis(5-tetrazolyl)-3-oxapentane (13)
4-Bis[2-(5-tetrazolyl)ethyl]amino-1,2,4-triazole (14)
Trihydric NH-acids
1,3,5-Tris(5-tetrazolyl)pentane (2)
3-Phenyl-1,3,5-tris(5-tetrazolyl)pentane (3)
3-(4-Nitrophenyl)-1,3,5-tris(5-tetrazolyl)pentane (4)
Bis[2-(5-tetrazolyl)ethyl]amine hydrochloride (7)
Tris[2-(5-tetrazolyl)ethyl]nitromethane (10)
Tetrahydric NH-acids
5.82±0.03
5.05±0.03
4.54±0.04
4.82±0.02
4.63±0.02
4.48±0.03
6.73±0.03
5.80±0.03
5.57±0.05
5.76±0.02
5.67±0.03
5.46±0.04
0.91
0.75
1.03
0.94
1.04
0.98
4.42
4.47
3.85
3.58
4.03
5.56
5.87
5.43
4.30
4.84
6.48
6.88
6.32
8.91
5.72
1.14
1.40
1.58
1.72
0.81
0.92
1.01
0.89
4.61
0.88
0.01
0.06
0.02
0.04
0.03
2,2,5,5-Tetrakis[2-(5-tetrazolyl)ethyl]cyclopentanone (1)
Bis[2-(5-tetrazolyl)ethyl]malonic acid (9)
2,2,6,6-Tetrakis[2-(5-tetrazolyl)ethyl]cyclohexanone (12)
4.32
3.08
4.82
5.19
5.22
5.75
5.85
6.23
6.35
6.79
8.40
7.32
0.87
2.14
0.93
0.66
1.01
0.60
0.94
2.17
0.97
0.05
0.05
0.03
_______
* NH-acids 2-4, 7-11, and 13 were titrated in 0.1 N solutions of NaNO3 at 25°C, NH-acid 5 in pure methanol, solutions of
NH-acids 1, 6, 12, and 14 in methanol–0.1 N aqueous NaNO3 solution, 50:50.
2
+1
n = pKan – pKan.
∆
*
*3 According to [11], pKa1 and pKa2 for ditetrazole 13 are 4.69 and 5.68 respectively, pKa1, pKa2, and pKa3 for ditetrazole 7
are 3.61, 4.32, and 8.89 respectively.
*4 Statistical error of calculation using the distribution function.

For the tetrahydric NH-acids 1 and 12 the values of ∆1 and ∆3 are close to one another and significantly
exceed ∆2. Probably those NH-tetrazole rings which are spatially close to one another dissociate first and
second. The dissociation of compounds 1 and 12 may be described by the following scheme.
N
N
N
N
_
N
N
_
N
N
N
N
N
N
N
N
N
N
N
N
HN
NH
HN
HN
N
N
H+
O
O
O
H+
- H+
H+
- H+
- H+
HN
NH HN
HN
NH
N
n
n
n
_
N
N
N
N
O
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
_
N
_
N
_
N
N
N
N
N
N
N
N
HN
N
N
N
O
H+
H+
- H+
- H+
N
N
N
N
n
n
_
_
_
_
N
N
N
N
N
N
N
N
N
N
N
N
The terminal tetrazole rings show significant mutual effects even at a distance. This may be caused by
electronic, spatial, or other factors, such as hydrogen bonds [15].
EXPERIMENTAL
1
The H and 13C NMR spectra were recorded on a Bruker AC-200 spectrometer (200 and 50 MHz
respectively) in DMSO, internal standard was the signal of the solvent. The IR spectra were obtained on a
Specord M-80 instrument in KBr disks. Elemental analysis was carried out on a Hewlett-Packard 185B
C,H,N-analyzer. Melting points were determined on a type PTP instrument with a heating rate of 1°C/min in the
melting range. Potentiometric titration was carried out on a pH 121 potentiometer (electrodes: glass EVL-1M3,
silver chloride ESL-63-07T4.1). All potentiometric measurements were carried out at 25°C in solutions of
constant ionic strength (0.1 N sodium nitrate solution).
The synthesis and physicochemical characteristics of tetrazoles 10-14 and of their nitrile precursors are
given in [1].
2,2,5,5-Tetrakis(2-cyanoethyl)cyclopentanone. Acrylonitrile (13.25 g, 250 mmol) was added
dropwise with cooling to a mixture of cyclopentanone (4.2 g, 50 mmol), benzyltriethylammonium chloride
(0.1 g, 0.5 mmol), and NaOH (0.02 g, 0.5 mmol) in 1,4-dioxane (30 ml) and water (2 ml) at such a rate that the
temperature of the reaction mixture did not exceed 40-45°C. The reaction mass was kept at room temperature
for 2 h, neutralized with dilute hydrochloric acid, the precipitated crystals were filtered off, washed with water,
and dried. The corresponding tetranitrile (13.6 g, 92%) was obtained as colorless crystals; mp 174-175°C
1
(acetone). H NMR spectrum, δ, ppm (J, Hz): 1.80 (12H, s, 2β-CH2 in cyclopentanone and 4CH2CH2CN);
1321

2.32 (8H, t, J = 14.6, CH2C≡N). 13C NMR spectrum, δ, ppm: 213.5 (C=O); 120.7 (C≡N); 49.7 (Cquat); 29.1
(β-CH2 in cyclopentanone); 28.1 (CH2CH2C≡N); 11.6 (CH2C≡N). IR spectrum, ν, cm-1: 2445 (C≡N), 1680
(C=O), 1550, 1460. Found, %: C 68.68; H 7.12; N 18.74. C17H20N4O. Calculated, %: C 68.89; H 6.80; N 18.90.
Attention. In view of the highly exothermal nature of the cyanoethylation reaction rapid addition of
acrylonitrile may lead to strong initial heating and ejection of the reaction mass.
3-Cyano-3-ethoxycarbonylpimelonitrile. Acrylonitrile (13.25 g, 250 mmol) was added dropwise with
cooling to a mixture of ethyl cyanoacetate (13.4 g, 100 mmol), benzyltriethylammonium chloride (0.1 g,
0.5 mmol), and NaOH (0.02 g, 0.5 mmol) in 1,4-dioxane (50 ml) and water (2 ml), at such a rate that the
temperature of the reaction mass did not exceed 40-45°C. The reaction mass was kept at room temperature for
1 h, neutralized with dilute hydrochloric acid, and poured into water (200 ml) cooled to 5°C. The oily liquid
insoluble in water was separated and dried in vacuum. The corresponding trinitrile (20.62 g, 86%) was obtained
1
as colorless crystals; mp 36-37°C (ethanol). H NMR spectrum, δ, ppm (J, Hz): 1.25 (3H, t, J = 7.3, CH3 in
OEt); 2.25 (4H, t, J = 7.3, CH2C≡N); 2.65 (4H, t, J = 7.3, CH2CH2C≡N); 4.22 (2H, q, J = 7.3, CH2 in OEt).
13C NMR spectrum, δ, ppm: 166.6 (C=O); 119.0 and 119.5 (C≡N); 63.4 (CH2 in OEt); 47.6 (Cquat); 30.9
(CH2CH2C≡N); 13.1 (CH2C≡N); 13.6 (CH3 in OEt). IR spectrum, ν, cm-1: 2250 (C≡N), 1740, 1695 (COO),
1470, 1440, 1355. Found, %: C 60.12; H 6.08; N 18.88. C11H13N3O2. Calculated, %: C 60.26; H 5.98; N 19.17.
3-Cyano-3-phenylpimelonitrile. Acrylonitrile (23.85 g, 450 mmol) was added dropwise with cooling
to a mixture of benzyl cyanide (11.7 g, 100 mmol), benzyltriethylammonium chloride (0.1 g, 0.5 mmol), and
NaOH (0.02 g, 0.5 mmol) in 1,4-dioxane (50 ml) and water (2 ml) at such a rate that the temperature of the
reaction mass did not exceed 40-45°C. The reaction mass was maintained at room temperature for 2 h,
neutralized with dilute hydrochloric acid, after which the precipitated crystals were filtered off, washed with
water, and dried. The corresponding trinitrile (10.5 g, 90%) was obtained as colorless needle-like crystals;
1
mp 69-70°C (ethanol). H NMR spectrum, δ, ppm (J, Hz): 2.30 (4H, t, J = 7.3, CH2C≡N); 2.60 (4H, t, J = 7.3,
13
CH2CH2C≡N); 7.80-8.50 (5H, arom.). C NMR spectrum, δ, ppm: 147.8, 142.5, 128.3, 124.6 (Ph); 119.3 and
119.0 (C≡N); 34.0 (CH2CH2C≡N); 13.1 (CH2C≡N). IR spectrum, ν, cm-1: 2240 (C≡N), 1630, 1475, 1450, 745.
Found, %: C 75.12; H 6.03; N 18.64. C14H13N3. Calculated, %: C 75.31; H 5.87; N 18.82.
3-Cyano-3-(4-nitrophenyl)pimelonitrile was obtained analogously to 3-cyano-3-phenylpimelonitrile
from 4-nitrobenzyl cyanide (7.6 g, 47 mmol) in a yield of 7.15 g (94%) as colorless needle-like crystals;
mp 147-148°C (ethanol). 1H NMR spectrum, δ, ppm (J, Hz): 2.30 (4H, t, J = 7.3, CH2C≡N); 2.60 (4H, t, J = 7.3,
CH2CH2C≡N); 7.80-8.30 (4H, arom.). 13C NMR spectrum, δ, ppm: 147.8, 142.5, 128.2, 124.5 (4-NO2C6H4);
119.5 and 119.0 (C≡N); 34.0 (CH2CH2C≡N); 13.0 (CH2C≡N). IR spectrum, ν, cm-1: 2240 (C≡N), 1630, 1525
(NO2), 1480, 1445, 760. Found, %: C 62.43; H 4.85; N 20.72. C14H12N4O2. Calculated, %: C 62.68; H 4.51;
N 20.88.
9,9-Bis(2-cyanoethyl)fluorene. Acrylonitrile (11.14 g, 210 mmol) was added dropwise with cooling to
a mixture of fluorene (16.62 g, 100 mmol), benzyltriethylammonium chloride (0.1 g, 0.5 mmol), and NaOH
(0.02 g, 0.5 mmol) in 1,4-dioxane (50 ml) and water (2 ml) at such a rate that the temperature of the reaction
mass did not rise above 40-45°C. The reaction mass was maintained for 2 h at ~20°C, neutralized with dilute
hydrochloric acid, the precipitated crystals were then filtered off, washed with water, and dried. The dinitrile
1
(12.0 g, 72%) was obtained as fine long colorless needle-like crystals; mp 118-119°C (ethanol). H NMR
spectrum δ, ppm (J, Hz): 1.57 (4H, t, J = 7.3, CH2CN); 2.43 (4H, t, J = 7.3, CH2CH2C≡N); 7.30-7.90 (8H,
arom.). 13C NMR spectrum, δ, ppm: 145.7, 140.7, 128.4, 128.0, 123.7, 120.5 (fluorene); 119.8 (C≡N); 53.4
(Cquat); 33.8 (CH2CH2C≡N); 11.7 (CH2C≡N). IR spectrum, ν, cm-1: 2235 (C≡N), 1650, 1635, 1480, 1450, 780,
745. Found, %: C 83.55; H 6.18; N 10.15. C19H16N2. Calculated, %: C 83.79; H 5.92; N 10.29.
1,2-Bis(cyanoethoxy)propane. A mixture of acrylonitrile (26.5 g, 500 mmol), 1,4-dioxane (25 ml), and
1,2-propanediol (19.02 g, 250 mmol) was stirred for 5 h at 45°C. The reaction mass was neutralized with dilute
hydrochloric acid, the dioxane was distilled off in vacuum, and the residue was distilled at 178-180°C
(5 mm Hg). The appropriate dinitrile (18.7 g, 41%) was obtained. 1H NMR spectrum, δ, ppm (J, Hz): 1.09 (3H,
1322

d, J = 5.0, CHCH3); 2.72 (4H, t, J = 5.8, CH2C≡N); 3.42 (2H, d, J = 5.0, CH2CHCH3); 3.64 (4H, t, J = 5.8,
CH2CH2C≡N). 13C NMR spectrum, δ, ppm: 119.4 and 119.3 (C≡N); 74.3 and 74.0 (CH2–CH); 65.6 and 63.6
(CH2CH2C≡N); 18.7 and 18.2 (CH2C≡N); 16.9 (CH3). IR spectrum, ν, cm-1: 2888 (CH2), 2240 (C≡N), 1470,
1410, 1200, 1135. Found, %: C 58.96; H 7.95; N 15.12. C9H14N2O2. Calculated, %: C 59.32; H 7.74; N 15.37.
Bis(2-cyanoethyl)amine. Acrylonitrile (95 g, 1.8 mol) was added dropwise with stirring and cooling
during 2 h to an aqueous solution of ammonia (950 ml, ~18 mol) saturated in the cold. The rate of addition was
regulated such that a second layer was not formed and the reaction temperature did not exceed 35°C. The
reaction mixture was maintained at ~20°C for a further 30 min, and the water distilled off in vacuum. The
residue was fractionally distilled. 2-Aminopropionitrile (375 g, 30%) and bis(2-cyanoethyl)amine (52 g, 47%)
were obtained, the latter as a viscous colorless liquid; bp 205°C (25 mm Hg). 1H NMR spectrum, δ, ppm (J, Hz):
2.65 (4H, t, J = 5.0, CH2C≡N); 3.60 (4H, t, J = 5.0, CH2CH2C≡N); 9.20 (1H, s, NH). 13C NMR spectrum,
δ, ppm: 119.1 (C≡N); 64.7 (CH2CH2C≡N); 18.5 (CH2C≡N). IR spectrum, ν, cm-1: 2300-2800 (NH), 2260
(C≡N), 1470, 1450, 1300. Found, %: C 58.59; H 7.64; N 33.87. C6H9N3. Calculated, %: C 58.51; H 7.37;
N 34.12.
Bis(2-cyanoethyl)amide of 4-Nitrobenzoic Acid. A mixture of 4-nitrobenzamide (16.6 g, 100 mmol),
benzyltriethylammonium chloride (0.1 g, 0.5 mmol), and NaOH (0.02 g, 0.5 mmol) in acrylonitrile (50 ml) was
cautiously heated to homogenization. An exothermal reaction was observed. The crystals precipitated after
cooling the reaction mass were filtered off, washed with water, and dried. The appropriate dinitrile (19.0 g,
1
70%) was obtained as colorless needle-like crystals; mp 148-150°C (ethanol). H NMR spectrum, δ, ppm
(J, Hz): 2.67 and 2.75 (4H, t, J = 7.3, CH2C≡N); 3.45 and 3.60 (4H, t, J = 7.3, CH2CH2C≡N); 7.85-8.20 (4H,
arom.). 13C NMR spectrum, δ, ppm: 169.1 (CON); 147.4, 142.5, 128.0, 122.6 (4-NO2C6H4); 118.9 (C≡N); 44.8
and 40.1 (CH2CH2C≡N); 16.2 and 15.6 (CH2C≡N). IR spectrum, ν, cm-1: 2240 (C≡N), 1770 (COO), 1610, 1530
(NO2), 1450, 1415, 760. Found, %: C 57.06; H 4.77; N 20.44. C13H12N4O3. Calculated, %: C 57.35; H 4.44;
N 20.58.
General Procedure for Obtaining Tetrazoles 1-8. A mixture of the 2-cyanoethyl derivative (25 mmol)
and a 10% molar excess of sodium azide and dimethylamine hydrochloride, calculated for each nitrile group in
the substrate, in DMF (50 ml) was heated to 110-115°C and left for 15-20 h. The precipitated solid sodium
chloride was filtered off, the filtrate evaporated, the residue was dissolved in water (100 ml), and the solution
acidified to pH <2 with dilute hydrochloric acid. The precipitated solid was filtered off, washed with water,
dried, and crystallized from ethanol or an ethanol–DMF mixture.
2,2,5,5-Tetrakis[2-(5-tetrazolyl)ethyl]cyclopentanone (1). Yield 8.65 g (74%); mp 215°C (decomp.,
1
EtOH–DMF). H NMR spectrum, δ, ppm: 1.95 (12H, s, 2CH2 in cyclopentanone and 4CH2CH2CN4H); 2.85
(8H, br. s, CH2CN4H); 14.8 (4H, br. s, CN4H). 13C NMR spectrum, δ, ppm: 214.1 (C=O); 155.9 (C(5) in
tetrazole); 51.3 (Cquat); 31.3 (CH2CH2CN4H); 30.0 (CH2 in cyclopentanone); 18.1 (CH2CN4H). IR spectrum,
ν, cm-1: 3000-3200 (NH), 1670 (C=O), 1560, 1420, 1250, 1105 (tetrazole). Found, %: C 43.28; H 5.45; N 47.62.
C17H24N16O. Calculated, %: C 43.58; H 5.16; N 47.84.
1
1,3,5-Tris(5-tetrazolyl)pentane (2). Yield 4.4 g (64%); mp 218°C (decomp., ethanol). H NMR
spectrum, δ, ppm: 2.20 (4H, br. s, CH2CH2CN4H); 2.80 (4H, br. s, CH2CN4H); 3.30 (1H, m, CH); 15.70 (3H,
br. s, CN4H). 13C NMR spectrum, δ, ppm: 158.0 and 155.4 (C(5) in tetrazoles); 38.2 (CH); 30.8 (CH2CH2CN4H);
18.2 (CH2CN4H). IR spectrum, ν, cm-1: 2800-3100 (NH), 1550, 1470, 1255, 1145, 1040 (tetrazole). Found, %:
C 34.52; H 4.64; N 60.41. C8H12N12. Calculated, %: C 34.78; H 4.38; N 60.84.
3-Phenyl-1,3,5-tris(5-tetrazolyl)pentane (3). Yield 7.05 g (80%); mp 224-225°C (decomp., ethanol).
1H NMR spectrum, δ, ppm: 2.50-3.00 (8H, m, CH2CN4H and CH2CH2CN4H); 7.15-7.50 (5H, m, Ph); 16.00 (3H,
13
br. s, CN4H). C NMR spectrum, δ, ppm: 161.3 and 155.6 (C(5) in tetrazoles); 141.9, 129.0, 127.6, 126.9 (Ph);
45.0 (Ph–C–CN4H); 34.4 (CH2CH2CN4H); 18.5 (CH2CN4H). IR spectrum, ν, cm-1: 2900-3200 (NH), 1630,
1550, 1475, 1450, 1255, 1135, 810 (tetrazole). Found, %: C 47.48; H 4.88; N 47.52. C14H16N12. Calculated, %:
C 47.72; H 4.58; N 47.70.
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3-(4-Nitrophenyl)-1,3,5-tris(5-tetrazolyl)pentane (4). Yield 8.12 g (82%); mp 210.5-211.5°C
1
(decomp., ethanol). H NMR spectrum, δ, ppm: 2.50-2.80 (8H, m, CH2CN4H and CH2CH2CN4H); 7.22-7.41
(4H, m, 4-NO2C6H4); 15.98 (3H, br. s, CN4H). 13C NMR spectrum, δ, ppm: 161.2 and 155.5 (C(5) in tetrazoles);
141.8, 128.9, 127.5, 126.8 (4-NO2C6H4); 67.2, 45.0 (Cquat); 34.3 (CH2CH2CN4H); 18.4 (CH2CN4H). IR spectrum,
ν, cm-1: 2900-3200 (NH), 1640, 1555, 1530, 1250, 1080, 790 (tetrazole). Found, %: C 41.93; H 4.10; N 45.57.
C14H15N13O2. Calculated, %: C 42.32; H 3.80; N 45.82.
9,9-Bis[2-(5-tetrazolyl)ethyl]fluorene (5). Yield 7.70 g (86%); mp 280°C (decomp., ethanol). 1H NMR
spectrum, δ, ppm (J, Hz); 2.05 (4H, t, J = 9.4, CH2CN4H); 2.52 (4H, t, J = 9.4, CH2CH2CN4H); 7.30-8.00 (8H,
arom.); 15.60 (2H, br. s, CN4H). 13C NMR spectrum, δ, ppm: 155.6 (C(5) in tetrazole); 147.4, 140.8, 127.9,
123.3, 120.4, 54.1 (fluorene); 36.5 (CH2CH2CN4H); 18.2 (CH2CN4H). IR spectrum, ν, cm-1: 2900-3100 (NH),
1640, 1550, 1465, 1250, 1100, 770 (tetrazole). Found, %: C 63.31; H 5.38; N 30.96. C19H18N8. Calculated, %:
C 63.67; H 5.06; N 31.27.
1
1,2-Bis[2-(5-tetrazolyl)ethoxy]propane (6). Yield 2.95 g (44%); mp 97-100°C (ethanol). H NMR
spectrum, δ, ppm (J, Hz): 1.08 (3H, d, J = 6.5, CHCH3); 3.05 (4H, t, J = 7.5, CH2CN4H); 3.28 (2H, d, J = 6.5,
CH2CHCH3); 3.50 (1H, m, J = 6.5, CH2CHCH3); 3.70 (4H, t, J = 7.5, CH2CH2CN4H); 15.80 (2H, br. s, CN4H).
13C NMR spectrum, δ, ppm: 154.1 (C(5) in tetrazole); 73.8 and 74.0 (CH2–CH); 67.6 and 65.5 (CH2CH2CN4H);
24.5 and 24.1 (CH2CN4H); 16.9 (CH3). IR spectrum, ν, cm-1: 3000-3200 (NH), 1605, 1570, 1550, 1450, 1340,
1250, 1120, 1050 (tetrazole). Found, %: C 39.98; H 6.27; N 41.56. C9H16N8O2. Calculated, %: C 40.29; H 6.01;
N 41.77.
Bis[2-(5-tetrazolyl)ethyl]amine Hydrochloride (7). Yield 4.17 g (68%); mp 152-154°C (decomp.,
1
ethanol). H NMR spectrum, δ, ppm: 3.05 (4H, br. s, CH2CN4H); 3.70 (4H, br. s, CH2CH2CN4H); 9.00 (1H, s,
NH); 16.00 (2H, br. s, CN4H). 13C NMR spectrum, δ, ppm: 154.3 (C(5) in tetrazole); 66.7 (CH2CH2CN4H); 23.5
(CH2CN4H). IR spectrum, cm-1: 3000-3200, 2200-2800 (NH), 1560, 1450, 1380, 1255, 1100, 950 (tetrazole).
Found, %: C 29.20; H 5.16; N 51.08. C6H11N9·HCl. Calculated, %: C 29.33; H 4.92; 51.31.
Bis[2-(5-tetrazolyl)ethyl]amide of 4-Nitrobenzoic Acid (8). Yield 5.07 g (85%); mp 73-74°C
1
(decomp., methanol). H NMR spectrum, δ, ppm (J, Hz): 3.00 and 3.12 (4H, t, J = 7.5, CH2CN4H); 3.60 and
3.82 (4H, t, J = 7.5, CH2CH2CN4H); 7.40 (2H, d, J = 4.0, 4-NO2C6H4); 8.22 (2H, d, J = 4.0, 4-NO2C6H4); 16.00
(2H, br. s, CN4H). 13C NMR spectrum, δ, ppm: 169.1 (CON); 154.0 (C(5) in tetrazole); 147.8, 142.4, 127.7,
123.9 (4-NO2C6H4); 46.5 and 42.3 (CH2CH2CN4H); 22.3 and 21.2 (CH2CN4H). IR spectrum, ν, cm-1: 2900-3200
(NH), 1760 (COO), 1645, 1550, 1535, 1250, 1100, 780. Found, %: C 43.14; H 4.15; N 38.73. C13H14N10O3.
Calculated, %: C 43.58; H 3.94; N 39.09.
Bis[2-(5-tetrazolyl)ethyl]malonic Acid (9). A solution of ditetrazole 11 (3.52 g, 10 mmol) and NaOH
(4.0 g, 100 mmol) in water (50 ml) was boiled for 10 h, cooled, and acidified to pH 1 with dilute hydrochloric
acid. The precipitated solid was filtered off, washed with distilled water, dried, and crystallized from ethyl
1
acetate. Compound 9 was obtained (2.52 g, 85%); mp 172-173°C (decomp., ethyl acetate). H NMR spectrum,
δ, ppm (J, Hz): 2.25 (4H, t, J = 7.0, CH2CN4H); 2.85 (4H, t, J = 7.0, CH2CH2CN4H); 8.00-18.00 (4H, br. s,
CN4H and COOH). 13C NMR spectrum, δ, ppm: 172.1 (COOH), 155.5 (C(5) in tetrazole); 56.0 (Cquat); 29.8
(CH2CH2CN4H); 18.6 (CH2CN4H). IR spectrum, ν, cm-1: 2900-3200 (NH and OH), 1760 (COO), 1645, 1550,
1535, 1250, 1100, 780. Found, %: C 36.05; H 4.22; N 37.54. C9H12N8O4. Calculated, %: C 36.49; H 4.08;
N 37.82.
The work was carried out with the financial support of the Ministry of Education of the Russian
Federation for fundamental investigations in the area of technical sciences (TOO 2-09.3-3222).
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